This invention relates to swimming pool filter systems and more particularly to such a system including an over-pressure alarm.
Conventional pool filter systems have a pump and a filter connected in a hydraulic loop with the pool.
The filter for large commercial pools is usually of the sand type wherein the water is pumped down through a bed of sand that collects the dirt from the water.
Smaller and less heavily used family pools, on the other hand, employ a low cost diatomaceous earth type filter wherein a finely woven membrane or the like that is water permeable separates the inlet chamber of the filter from the outlet water chamber, and the inlet side of the membrane is coated with diatomaceous earth which cannot pass through the membrance but collects dirt.
In either system employing a sand filter or a diatomaceous earth filter represented in FIG. 1 a pressure gauge 11 is normally installed at the inlet port of the filter 13 providing a pressure reading that increases as the filter collects more dirt and restricts the water flow through the filter 13. The supplier of the filter system normally recommends back washing the filter to remove the dirt when the pressure gauge indicates a high pressure of a predetermined value. Backwashing requires additional pipes and valves not shown here, for reversing the flow of water through the filter while flushing the dirt and diatomaceous earth to the outside.
In one diatomaceous earth filter, Model No. EC-65 System III made by Hayward Pool Products, Inc. of Elizabeth, N.J., removal of the dirt is not accomplished by back washing but rather by moving and shocking the membrane to redistribute the diatomaceous earth in the inlet chamber of the filter and, with the inlet and outlet ports shut closed, draining the inlet chamber. Such a cleaning and dirt removal operation is said to take about 5 minutes and should be done when the inlet port pressure gauge rises more than 10 psi (pounds per square inch) in less than a 24 hour period or when cloudy water returns to the pool for longer than 30 seconds after a "regeneration" step.
The frequency at which the filter must be cleaned by the above-noted cleaning/draining step in this system is substantially less than that for a more conventional diatomaceous earth filter system having only the capability of being backwashed because the Hayward filter can be regenerated, i.e. agitated, by shocking the movable filter membrane relative to the filter housing, each time the pressure rises to within 7 to 10 psi above the pressure read just after the last cleaning operation. During this simple regeneration, the clogged cake is shaken off of the membrane so that the dirt having coated the diatomaceous earth coating, and the diatomaceous earth itself, are redistributed, before resuming normal pumping and filtering and recoating the membrane with the more permeable redistributed mixture of dirt and diatomaceous earth.
Under normal operation this system typically should be regenerated every two or three days, while draining to clean the filter is needed only after 3 to 10 weeks by the above-noted criteria. However, these times vary greatly with pool usage and weather conditions.
In practice, a family pool filter system is only checked when some one of the family members happens to think about it, and the chances are especially great that both regeneration and draining to clean the filter will be done too infrequently. This is particularly true after hot summer days when algae, if any, grows faster and pool usage is generally high, both increasing the dirt load to be filtered and drastically increasing the frequency of regeneration that is needed. Furthermore, besides the deteriorating condition of the swimming pool water, the pump will run inefficiently and uselessly. And in those systems wherein chloride is automatically dispensed into the water conduits from the pump to the pool, the pool can turn green with algae within hours on a hot day of high usage when water flow is blocked by a clogged filter.
It is, therefore, an object of the present invention to provide in a diatomaceous-earth pool-filter system of the regeneration type, an alarm that is activated when regeneration and/or cleaning is needed.
It is a further object of this invention to provide such a pool filter system wherein the number of regenerations executed is automatically counted, so that the count from the time of the previous filter cleaning operation may be used as an indication of the need for the next filter cleaning operation.